Improvement of Fretting Fatigue Strength by Using Stress-Release Slits

A new estimation method for fatigue crack initiation criteria using plain fatigue limit, threshold stress intensity factor range, and specific depth is proposed. Using this, new design method for improving fretting fatigue strength have been developed by using stress-release slits on the pads near the contact edges. This design has analyzed on the basis of stress singularity parameters at the contact edges, and the analysis results were used to optimize the slit shapes, such as slit depth and slit position.This optimization takes into account the fretting fatigue crack initiation strength at the contact edge and the fatigue strength at the slit root. We confirmed that the fretting fatigue crack initiation strength of the optimized design is about twice that of a conventional (i.e., slitless) design.